Adults are 18 cm (7 in) long and have black and white stripes on their head, a gray face, brown streaked upper parts and a long tail. The wings are brown with bars and the underparts are gray. Their bill is pink or yellow. They are similar in appearance to the white-throated sparrow, but do not have the white throat markings or yellow lores.

There are five currently recognized subspecies of white-crowned sparrow (pugetensis, gambelii, nuttalli, oriantha, and leucophrys), varying in breeding distribution migratory route. Birds of the subspecies nutalli are permanent residents in California, while birds of the subspecies gambelli may migrate as far as the Arctic Circle during the summer breeding season. Northern birds migrate to the southern United States.

These birds forage on the ground or in low vegetation, but sometimes make short flights to catch flying insects. They mainly eat seeds, other plant parts and insects. In winter, they often forage in flocks.

White-crowned sparrows nest either low in bushes or on the ground under shrubs and lay three to five brown-marked gray or greenish-blue eggs.

The white-crowned sparrow is known for its natural alertness mechanism, which allows it to stay awake for up to two weeks during migration.[8] This effect has been studied for possible human applications, such as shift-work drowsiness or truck driving.[9][10][11]